The invention relates to a stator for an electric multiphase motor, particularly a stepping motor with a ring housing and pole pieces arranged in star-like fashion which can be inserted therein and can be wound from the outside, having axially integral pole pieces which are arranged in star-like fashion around a hollow cylinder and are inserted into the latter, in general and more particularly to an improved stator of this nature.
In one known stator of this type (German Offenlegungsschrift No. 1 814 977) the pole pieces sit with their one end in a hollow cylinder of plastic; for this purpose, they extend into the hollow cylinder up to a certain radial depth, so that either a circular intermediate layer of plastic remains between the radially inner limit of the pole pieces forming the legs of the star and the air gap proper, or the hollow cylinder must be turned from the inside in a further operation in order to obtain a particularly small air gap between the legs and the rotor. The fabrication and the joining of the hollow cylinder to the legs is accomplished in a single operation by a compound sraying process. The pole pieces of the star consist of solid material and have bevelled end faces, so that each pole piece is trapezoidal. The end faces of the pole pieces may be straight lined or curved at an angle. A coating of plastic may also be applied to the end faces of the pole pieces. The pole piece star fabricated in this manner is pushed into a ring housing and is fastened and solidified with the former and in itself by casting with the casting resin.
In a further stator described in U.S. Pat. No. 2,607,816, the pole piece star is laminated in such a manner that a multiplicity of pole piece laminations are stacked congruently and secured to each other, for instance, by screws. Each individual pole piece star lamination is integrally stamped from sheet metal in such a manner that the teeth extending in the radial direction are formed onto an inner laminated hollow cylinder; the laminated hollow cylinder connects the teeth at the radially inner end and, thus forms magnetic bridges between them. The pole piece star, which is stacked from the individual laminations and is fastened together by axially extending screws is inserted into a closed ring housing, or partial ring housing segments are inserted between the radially outer ends, and are welded to the radially outer ends of the pole piece teeth for solidification.